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Pfizer’s Erectile Dysfunction Claim for Viagra® Found Invalid

On February 12, 2010, the Board of Patent Appeals and Interferences (BPAI) of the U.S. Patent and Trademark Office (USPTO) issued an decision invalidating Pfizer’s broad claim for treating male erectile dysfunction (ED). U.S. Patent No. 6,469,012, entitled “Pyrazolopyrimidinones for the Treatment of Impotence” issued on October 22, 2002 and assigned to Pfizer, Inc. (NYSE: PFE). The patent issued from U.S. Patent Application No. 08/549,792, filed March 4, 1996, which is the national phase of PCT/EP94/01580, filed May 13, 1994, and which claims benefit to GB Patent Application No. 9311920, filed June 9, 1993. The patent claims cover the first commercially successful male impotence drug — Viagra®. Immediately after the decision was handed down Pfizer spokesman, Chris Loder, said “the decision has no effect on Pfizer’s patent claims relating to Viagra.” Loder also said Pfizer would appeal the decision. As yet there remains no word on an appeal by Pfizer.

This patent was subject to four ex parte reexamination proceedings and five reexamination requests. The first reexamination was ordered sua sponte by the USPTO, which in itself is a rather unusual occurrence, while the other three were requested by Lilly ICOS (manufacturers and marketers of the competitor impotence drug Cialis®) and Bayer (manufacturer and marketer of another competitor impotence drug Levitra®). The four granted reexaminations were merged and the fifth request was denied as it did not add anything to the merged reexamination.

The claim at issue in the merged reexamination proceeding was:

Claim 24. A method of treating erectile dysfunction in a male human, comprising orally administering to a male human in need of such treatment an effective amount of a selective cGMP PDEV inhibitor, or a pharmaceutically acceptable salt thereof, of [sic] a pharmaceutical composition containing either entity.

Pfizer sued Lilly and ICOS in 2002 asserting that Cialis® infringed the ’012 patent (Pfizer Inc., et al. v. Lilly ICOS LLC et al., Civil Action No. 02-1561 (D. Del. Oct. 22, 2002)). Since 2003, this litigation has been stayed pending the decision on the reexamination(s). Certainly, if claim 24 were found to be valid, it would appear that administering any selective cGMP PDEV inhibitor, including compounds such as Cialis® and Levitra® would infringe this claim. Chemically, Cialis® (pyrazino-pyrido-indole-diones) and Levitra® (2-phenyl-imidazotriazinones) belong to different classes of compounds. However, they are also selective cGMP PDEV inhibitors so would fall under the broadly written claim 24.

The ’012 patent contains other claims that were not at issue, including method claims for the general class of compounds that sildenafil (the active compound in Viagra®) belongs to, namely pyrazolo-pyrimidinones. Therefore, it is at least somewhat true, that the decision does not directly impact Viagra®. However, if the invalidity of this claim is upheld on appeal, the best that Pfizer can do is to go after companies that make generic versions of sildenafil, which would be good news for Cialis®. Even before the verdict, Cialis® sales in the U.S. were up 16 percent to $149.4 million, while Viagra® was up only 4 percent at $207 million.

In the opinion, the BPAI agreed with the reexamination Examiner that any one of four (out of five) prior art references that contained descriptions of oral administration of the herb Yin Yang Huo (also known, perhaps not too surprisingly, as horny goat weed) are anticipatory prior art for claim 24. There were other rejections (double patenting) that the Examiner set forth and that the BPAI upheld.

The Examiner’s position was that a compound known as icariin is an ingredient of Yin Yang Huo and that icariin is a selective cGMP PDEV inhibitor. Pfizer’s position was that none of the Yin Yang Huo references identify which compound in Yin Yang Huo is responsible for the treatment of impotence; in other words Pfizer claimed none of the Yin Yang Huo references is enabled. Because it was undisputed that the Yin Yang Huo references disclosed treating impotence by oral administration of Yin Yang Huo, and that icariin is an active component of the Yin Yang Huo, the BPAI determined that the pertinent issue was whether the Yin Yang Huo references disclosed treating ED by administering an effective amount of icariin.

The Board found that the Yin Yang Huo references did indeed disclose treating ED by administering an effective amount of icariin. Pfizer argued that the amounts of Yin Yang Huo that the references stated that a man should take would result in very little inhibition of the specific enzyme that regulates blood flow in the penis. However, because claim 24 was so broad, the BPAI made clear that “the selective PDEV inhibitor of claim 24 is not required to have a minimum % inhibition at its IC50 or a maximum Ki or other enzyme kinetics inhibition value or other defined parameter that would exclude Yin Yang Huo from the claimed method.” In other words, the breadth of the claim was its downfall.

The Author

Gene’s particular specialty as a patent attorney is in the area of strategic patent consulting, patent application drafting and patent prosecution. He has worked with independent inventors and start-up businesses in a variety of different technology fields, but specializes in software, systems and electronics.

Gene is admitted to practice law in New Hampshire, is a Registered Patent Attorney licensed to practice before the United States Patent Office and is also admitted to practice before the United States Court of Appeals for the Federal Circuit.

Gene is a graduate of Franklin Pierce Law Center and holds both a J.D. and an LL.M. Prior to law school he graduated from Rutgers University with a B.S. in Electrical Engineering.

Warning & Disclaimer: The pages, articles and comments on IPWatchdog.com do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author and should not be attributed to the author’s employer, clients or the sponsors of IPWatchdog.com. Read more.

Discuss this

There are currently 5 Comments comments.

Steve MMarch 17, 2010 3:04 pm

Ah but for the fervent wish now of a continuation . . . and a handful of Huo-traversing dependent claims . . . and greater claim diversity.

American CowbouMarch 18, 2010 9:15 am

Stiffed by the Fed. Cir.

NatalieMarch 31, 2010 9:58 pm

This is just another lawsuit battle which will go nowhere but cost these companies millions of dollars.

Cost of ViagraNovember 25, 2010 2:25 am

Pfizer will of course defend their product. Of course they have to spend millions just to clear their names. Well, we cannot blame them because Viagra is very hot in the market. Thank you for sharing.

Earl CageFebruary 13, 2011 10:46 pm

One famous philosopher once stated that (There is no good nor bad, but thinking makes it so). There are some physical conditions that prevents some individuals from getting an erection, but I believe that most of are problems are first created in our minds. If I think I can, then I can, but If I think I can’t then I can’t. Eat healthy, exercise, and laugh a lot

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